1. Field
Example embodiments relate to infrared detectors, and more particularly, to infrared detectors configured to absorb broadband infrared light.
2. Description of the Related Art
According to the black body radiation theory, an object radiates a broadband electromagnetic wave, the intensity of the radiation being maximized at a specific wavelength that varies depending on a temperature of the object. For example, an object at room temperature radiates infrared light whose intensity is maximized at a wavelength of about 10 μm.
A bolometer is a device for measuring radiant energy by using the black body radiant theory. The bolometer absorbs an electromagnetic wave having a wavelength of radiated infrared light (or terahertz) and measures the radiant energy by converting the electromagnetic wave to heat and detecting a temperature change due to the heat.
Recently, with the development of microelectromechanical system (MEMS) technology, infrared detectors having a two-dimensional array of a plurality of microbolometers have been developed. Such infrared detectors may be used in, for example, a thermal imaging camera for obtaining thermo images. In order to manufacture a thermal imaging camera having high resolution and high temperature accuracy, it may be desirable to reduce a size of a pixel. However, when the infrared detector uses a bolometer having a Salisbury screen structure, in which a ground plate is spaced apart from a thermal absorber by a distance of λ/4 (where, λ is a center wavelength of a wavelength band of infrared light to be detected), if a size of a screen within a pixel is reduced, incident energy on each pixel may decrease. By decreasing the incident energy provided to each pixel, an amount of temperature change may decrease and a signal-to-noise ratio may also decrease.
Surface plasmon is a type of electromagnetic wave generated due to charge density oscillation occurring at a surface of metal rather than internally as in a Salisbury screen. A bolometer utilizing a localized surface plasmon resonance (LSPR) phenomenon instead of the Salisbury screen structure has been recently proposed. A bolometer using a plasmonic absorber may overcome the limitations of the low absorbing rate and the low signal-to-noise ratio because of the LSPR.
However, since the plasmonic absorber has a relatively narrow bandwidth, it is difficult to obtain thermo images. Therefore, various methods of increasing a resonance bandwidth of the plasmonic absorber are proposed.